The quality of elastomeric products, such as seals, may be affected by various factors such as variations in dimensions, non-uniformities or overall substandard properties of resilience or hardness, subsurface as well as surface defects such as inclusions, voids, tears, and the like.
Surface defects, or variations in the dimensions of such articles can be detected visually or by using automated profilometry, optical, or other techniques. However, such techniques do not detect subsurface defects, non-uniformities or overall substandard properties of the material.
Other techniques, such as ultrasonics and radiography, that are used for detecting subsurface defects in certain other materials, have serious disadvantages when applied to polymeric materials due to the high damping and small density variations that a defect represents in such a material.
Prior to the making of the present invention, a technique somewhat analogous to a method known for the testing of tires was tried. This involved placing an O-ring to be tested on a rim of matched size and detecting variations in load when rolled against a roller under pressure. This approach, however, was found not to be satisfactory. The use of a rim produced spurious results that were seen to be caused be effects related to the combined structure of the O-ring and rim, for example, due to slipping and folding along the O-ring to rim interface.
Also, this approach necessitated stretching of the O-ring onto the rim which could not be done completely uniformly and which effectively masked any material defects close to the rim while accentuating any rim defects. It was also impractical for testing O-rings of many sizes, with a new rim being necessary for each new size.